In 1937, at the height of the Great Depression, Jay C. Hormel had an idea that would change the way America eats. For decades, his family’s Minnesota meatpacking company had discarded thousands of pounds of pork shoulder deemed unworthy of the effort required to cut it off the bone. But Jay, the company’s president, wagered that cheap labor could be combined with cheap meat to create a new source of profit. At his instruction, Hormel’s meat scientists devised a system for cooking the loose scraps of pork shoulder into a loaf, packaged it in a modern-looking square can, and gave it a catchy name: Spam. Within three years, Hormel’s canned meat product was being eaten in 70 percent of American households.

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War presented an even bigger opportunity. After the Japanese bombed Pearl Harbor, Hormel secured a contract to supply Spam to every hungry GI around the world. But now Jay had a brand-new problem: supply. If the company was going to keep pace, it needed to increase production, which meant it needed more pork. Jay invited a group of medical researchers from the University of Minnesota to his estate and proposed turning a large horse barn on the grounds into a laboratory space, where researchers could work on finding ways to improve hog production—making the animals bigger and fatter as quickly as possible. A year later, Jay announced the opening of the Hormel Institute, where the dangerous modern practice of feeding antibiotics to pigs and other livestock—not to cure illness but to increase their growth rate and squeeze them into increasingly crowded conditions—was born.

"The increasing populations of swine raised in densely populated CAFOs and exposed to antibiotics presents opportunities for drug-resistant pathogens to be transmitted among human populations."

The institute started small, with a single researcher. But in 1945, with the war over and demand for cheap meat still soaring, its staff was expanded to eight, including Lawrence E. Carpenter, a newly minted Ph.D. from the University of Wisconsin. That same year, Carpenter’s former botany professor, Benjamin Duggar, took a job with American Cyanamid in Pearl City, New York. There Duggar developed a drug he named aureomycin, from the Latin for gold (aureus) and fungus (mykes). Aureomycin had the potential to be a wonder drug on the scale of penicillin; in hospital tests, it proved effective at fighting everything from whooping cough to typhus. But doctors found it was especially good against amoebic dysentery and other intestinal infections. And it had an interesting side effect: The patients put on weight.

One of Duggar’s colleagues at American Cyanamid wondered if aureomycin would have the same effect on livestock, so he tried it on chickens. Bingo: The test chicks grew as much as 50 percent larger than the control group. At the Hormel Institute, young Carpenter was eager to test his former professor’s discovery on hogs, so he obtained samples of the drug. By April 1950, he had conclusive evidence that a daily dose of the antibiotic could more than double feed efficiency. Carpenter announced the results in the Hormel Farmer, the free newsletter sent out to all of the company’s hog suppliers. By June, small town newspapers across Iowa and Minnesota were running advertisements touting aureomycin as “the most important advancement in Swine Nutrition in the last 25 years.” Soon, even the Wall Street Journal was reporting that 85 percent of runts “given aureo in their feed survived and grew up into self respecting hogs.” Lester E. Corson of Lyle, Minnesota, told a reporter that he had decided to try the supplement with his runts. “Now they actually look like they are going to make good market hogs.”

By the end of 1951, Jay Hormel told shareholders that the company’s Austin plant was nearing capacity in terms of the animals it could process in a day, but he foresaw continued growth in the number of pounds of pork they could produce each year, thanks to antibiotics. Not only was aureomycin allowing hogs to be “brought to marketable weight more quickly,” but now Hormel scientists were experimenting with weaning piglets sooner—and even feeding them artificial milk, laced with antibiotics, that could replace the natural immunity built up by breastfeeding. Jay envisioned a future where sows could give birth and go directly back into breeding. “This could mean that they might immediately be put back to work producing another litter,” Hormel said, “instead of consuming 8 pounds of feed a day for 56 days, performing no other service than can be performed by the milking machine at the nearest dairy.”

WHAT LOOKED LIKE A dream come true to Hormel and his stockholders has, in the 65 years since, transformed U.S. livestock production into a nightmare of overcrowded conditions and a breeding ground for “superbugs”—antibiotic-resistant bacteria that grow in the guts of swine and other animals, then pass into the human population via hog manure.

Last fall, the Centers for Disease Control and Prevention warned that antibiotic resistance was responsible for 14,000 U.S. deaths every year and rising, and said there was a very real chance antibiotics could lose all effectiveness if doctors didn’t stop over-prescribing them to patients and farmers didn’t cut back on feeding them to livestock for growth enhancement. This summer, CDC Director Thomas Frieden warned that drug-resistant bacteria could bring about “the next pandemic.”

“Because of the link between antibiotic use in food-producing animals and the occurrence of antibiotic-resistant infections in humans,” the CDC’s report said, “antibiotics should be used in food-producing animals only under veterinary oversight and only to manage and treat infectious diseases, not to promote growth.”

Good advice, but the CDC’s guidance—as well as standards issued by the federal Food and Drug Administration—remain voluntary, and public health advocates like the ones at NRDC (which publishes OnEarth) believe they will be inadequate to stop the spread of superbugs. “About 80 percent of all the antibiotics sold in this country today are for use in the livestock and poultry industries,” says Avinash Kar, an NRDC attorney who led a lawsuit seeking to force the FDA to take action against the practice. “Do we really think the pharmaceutical industry is going to voluntarily walk away from such a big chunk of its customer base? I don’t see that happening.”

As far back as the 1950s, Hormel’s own researchers had sounded a note of caution about the overuse of antibiotics. Lawrence Carpenter himself recorded that aureomycin was believed to encourage weight gain by wiping out intestinal microbiome that might otherwise compete with the nutrients in the hog’s digestive tract. Because the uptake of the antibiotic was focused on the gut, he wondered if the aureomycin might be passing through the hogs and into the manure that farmers were being encouraged to use as natural fertilizer. To mitigate this effect, he experimented with injected antibiotics but found “that aureomycin, administered either orally or by injection, is excreted in the feces of pigs.”

Researchers hoped this might not pose a problem; if aureomycin wiped out all bacteria in a hog’s digestive tract, then the feces might actually emerge as a safer manure. It might even produce hogs free from disease. But researchers at the University of Illinois soon discovered just the opposite: For the first nine days of receiving the antibiotic, they found, there was “a marked decrease in the coliform organisms in the feces of the pigs,” but after that the levels began to equalize until, at 16 days, “this difference had disappeared.” This data sequence suggested that antibiotic-resistant E. coli were breeding inside the pigs’ intestinal tracts, yielding a manure laced with super bacteria. And already three physicians at the University of Illinois College of Medicine reported: “Although aureomycin has been in general use for only three years, there is evidence that resistant strains of staphylococci are appearing in hospitalized patients.”

IN 2008, U.S. HOG farmers began reporting a rash of methicillin-resistant Staphylococcus aureus, known as MRSA. The bacteria often takes hold in humans via minor skin infections, but because it is resistant to antibiotics, it can lead to pneumonia or life-threatening infections of the bloodstream. Health officials worried that the illness, which was already prevalent among hogs in Europe and other parts of North America, had spread to herds in the United States and could jump to human hosts. A representative for the National Pork Producers Council told a reporter for the Seattle Post-Intelligencer that there was “nothing to worry about.” No cases of MRSA had been found among pigs on “this side of the border,” he said, claiming that the USDA and CDC had issued “our pigs a clean bill of health.” But the CDC immediately denied having ever made any such statement.

In fact, Tara Smith, then an assistant professor in the University of Iowa Department of Epidemiology, was in the midst of conducting the first scientific test of hogs for MRSA in the United States—and the findings were not nearly as reassuring as the Pork Council had suggested. Members of Smith’s team had swabbed the noses of 209 pigs from 10 hog barns in Iowa and Illinois and found MRSA present in 70 percent of the animals. More disturbingly, two of Smith’s graduate students also took swabs from 20 workers at several Iowa farms and found that 45 percent of the workers were also culture positive.

Spam may no longer dominate the American dinner table, but the practice it birthed—using drugs to produce ever-bigger animals—affects all of us now more than ever.

Because the bacteria live primarily in the nose and respiratory system, Smith undertook another study—this time in partnership with Margaret Carrel, a specialist in the geography of infectious disease at the University of Iowa—to investigate whether MRSA might be spreading to people beyond the confines of the hog barns. The team gathered the records of more than a thousand patients from rural Iowa who had been admitted to the Iowa Veterans’ Affairs Hospital with respiratory complaints in 2010 and 2011. In all, they found that 119 of the patients were suffering from MRSA. That rate in itself was distressingly high, but the greatest shock came when the home addresses for those patients were overlayed onto the Iowa state government’s map of CAFOs, or confined animal feeding operations (a.k.a. factory farms). The overwhelming number of patients with MRSA lived within one mile of a hog confinement. They were three times more likely to have the antibiotic-resistant bacteria than other residents of rural Iowa—and nearly 10 times more likely than someone living in an urban area.

The researchers were unable to say exactly how MRSA was making the jump from the confined hogs to the workers in the barns and the nearby residents, but they noted that manure from CAFOs is typically spread as fertilizer on the corn and soybean fields surrounding the barns. “MRSA can be aerosolized from this manure to human food or water sources,” they concluded. “The increasing populations of swine raised in densely populated CAFOs and exposed to antibiotics presents opportunities for drug-resistant pathogens to be transmitted among human populations.”

When I visited New Fashion Pork, one of Hormel’s biggest hog suppliers, last year to report on the industry for OnEarth, CEO Brad Freking told me that he simply didn’t believe that antibiotics could be passing through his hogs and producing resistant bacteria in his waste pits. “A lot of those antibiotics are broken down within the pig by the time it goes through the liver and the kidney. What the pig is actually urinating into the pit is a changed molecule. You see where I'm going?” he asked rhetorically. “If I put tetracycline into the pig, what is that molecule that comes out? Then, it sits in an active pit. Does it get broken down or changed again? I don’t know.”

But recent research indicates that as much as 80 percent to 90 percent of tetracyclines and other common antibiotics are still in active form when excreted by hogs. And far from hostile environments to bacterial growth, waste pits have been shown to be an ideal breeding ground for antibiotic-resistant strains of E. coli and S. aureus. Officials from the Des Moines Water Works assured me that their filtration systems, and those used in most local municipal water treatment plants, do an excellent job of removing antibiotics and bacteria from the water supply. But those downstream systems do nothing for people taking their water from wells near hog confinements or who live in homes neighboring fields where the application of manure releases antibiotic-resistant bacteria—and other contaminants—into the air and soil. The University of Iowa researchers were unequivocal: “Our study indicates that residential proximity to large numbers of swine in CAFOs in Iowa is associated with increased risk.”

Hormel Foods has responded to these concerns by putting the onus back on the federal government. In a public statement issued last year, the company said employs licensed veterinarians to prescribe only FDA-approved medications and dosage levels. “The FDA has the authority to ban any animal drug it feels poses a risk to human health,” the statement noted. Hormel also notes that the company participates in the National Pork Board’s “Take Care—Use Antibiotics Responsibly” campaign, but the program has no requirements (or even recommendations) about the use of antibiotics as growth-enhancers.

Spam may no longer dominate the American dinner table, but the practice it birthed—using drugs to produce ever-bigger animals—affects all of us now more than ever. A recent study commissioned by Consumer Reports found that nearly two-thirds of pork products sold in America’s grocery stores are contaminated by antibiotic-resistant strains of Yersinia enterocolitica, Staphylococcus, Salmonella, and E. coli. “It’s getting harder and harder for the food-processing industry and the FDA to ignore the fact that the overuse of antibiotics in animals is threatening public health,” Congresswoman Louise Slaughter of New York, herself a microbiologist, said in response to those findings. But until the government gets tough or the crisis affects the bottom line, it appears that superbugs are going to remain on the menu.

This post originally appeared on OnEarth as “This Little Piggy Bred a Superbug” and is republished here under a Creative Commons license.